A hard to identify odor. It wasn't rotten eggs.(natural gas leak) but more FUNKY almost recognizable odor....like body sweat? Yeah I know what it is.
In the basement of MOST homes there is a floor drain. It may have a round chrome cover over it that is about 6" in diameter and has a bunch of smaller holes (about 1/8" in size drilled through the metal so it lets water drain down it.) There are other styles some are a number of plastic bars that go across the opening and it is still about the same size. This is the floor drain. Usually positioned between the water tank and the laundry sink or the downstairs bathroom. Where ever water may leak out. This plumbing has a Pee trap just like every sink in the house or shower or toilet. Having water in there keeps the Pee smell of the sewer or septic tank gases in the sewer and allows for water to flow.
When there blockage (in this case the water) evaporates as it eventually does, in a concrete floor it may take a few years. then the sewer gas puffs out everytime you use a sink or flush a toilet.
That is the smell you smell. It is a combination of Shampoo, hairconditioner, soap, laundry soap, bleach, poo, pee, barf, rotting food if you have a garbage disposal then that is in there too, Lysol and body sweat.
. That is all it is.
How to fix. Grab a cup of water and pour it down every drain in the house. Some people never use their guest shower because they never have guests so it is used as a closet for clothes. It has a drain for water so it has a pee trap. I have seen people use the dried out toilet to store kids toys or their shoes in there. The toilet bowl is a Pee trap . It must have water in the bowl to close the stink. If your laundry room is like mine there is no water in the laundry tub as the 2 faucets are connected to the washer...so the laundry tub drain is dry.
Every drain in your house gets filled with water. Toilet bowls take more than 1 cup....but every sink, and shower and tub drain takes 1 cup of ordinary water.
. Do that once a year and you will never have the problem again. or put a plug in the drain and it slows down the evaporation process. Once a year is not a big deal or even more often and you are always safe.
45+ year home handyman.